It's not that simple...While it's true the plants use a lot of blue and red, the plants need a broader spectrum of light than just red or just blue. They also use different wavelengths for veggin vs. flowering. You can't hardly beat the spectrum of an MH bulb for veggin and an HPS bulb for flowering tho. We are experimenting with a new induction light which seems mostly blue and reddish...strange lookin bulb and all!